Beetle with long ‘nose’—A bizarre stem scydmaenine in amber from Myanmar (Coleoptera: Staphylinidae: Scydmaeninae)

Abstract

The staphylinid subfamily Scydmaeninae is a diverse assemblage of small predaceous beetles, represented by some 5360 extant and 51 extinct species. Recent explorations of Mesozoic scydmaenine fauna in Burmese, Canadian, French, and Spanish ambers have shed intriguing light on the early evolution, systematics, and particular aspects of predator-prey relationship among this group. However, in contrast to extant diversity, well-preserved fossils allowing for sufficient morphological studies and ecological reconstructions are extremely rare. Here we report a highly advanced glandulariine scydmaenine, Nuegua elongata Yin, Cai & Newton, gen. et sp. nov., based on a large series of fifteen exquisitely preserved specimens entombed in mid-Cretaceous Burmese amber. The new genus strikingly displays an extremely prolonged preocular region that accounts for over half of the head length—a structure unknown among all known living and extinct scydmaenines, but analogous to that of certain groups of the modern Laemophloeidae, Curculionoidea, Salpingidae, and Staphylinidae. We provide a formal description of the new genus, compare it with the most probably related taxa, and discuss possible functions of this bizarre head elongation. The discovery highlights the morphological disparity and palaeodiversity of the subfamily Scydmaeninae in late Mesozoic.